Furnace structure embodying multilayer fuel feeding



July 31, 1956 M. BIRKNER 2,756,700

FURNACE STRUCTURE EMBODYING MULTI-LAYER FUEL FEEDING Filed Nov. 24, 1950 I "III! 9 WWW INVENTOR. 777ax .B/r/(ner FURNACE STRUCTURE EMBODYING MULTI- LAYER FUEL FEEDING Max Birkner, Koln-Dellbruck, Germany Application November 24, 1950, Serial No. 197,263 Claims priority, application Germany November 25, 1949 6 Claims. (Cl. 110113) The present invention relates to a multilayer fuel charging device. More particularly the invention relates to a fuel charging arrangement combining a mechanical fuel feeding device and pneumatic fuel feeder in order to obtain maximum feed with the expenditure of a minimum amount of energy and regardless of the grain size of the coal to be burned. The invention further relates to a fuel feeding arrangement combining a separating grate with the fuel passage to screen the fuel and pass the smaller particles to the pneumatic feeder.

Fuel feeding arrangements for furnaces utilizing plural layer charging are known in the art in which a rearwardly travelling grate the upper run of which moves from the rear to the front of the furnace and which discharges ashes at the front of the furnace, is charged by fuel feeding means that feed the fuel from the front to the rear of the furnace and in which arrangements the finer grain particles are largely burned in suspension. It is also known in fuel feeding to utilize pneumatic charging devices wherein the fuel is blown by compressed air fromthe front of and into the burning space of the furnace. Such devices likewise utilize a travelling grate moving from the front of the furnace toward the rear and in connection with such conventional pneumatic feeding arrangements in contrast to mechanical or throw feeding, there is required a higher or greater expenditure of energy.

First of all the prior art feeding arrangements, more particularly the pneumatic type, are adapted for use with fuels with a high content of volatile particles usually above 20 per cent and which shows a grain size distribution wherein about one half of the grains are 0.5 mm. and above that are coarser grains up to 25-30 mm.

In charging a furnace by a mechanical throw shovel or feeder, the coarser coal particles are hurled a greater distance than the finer ones and for this reason the upper run of the travelling grate moves from the rear to the front of the furnace to provide more time for burning of the coarser particles.

In fuel feeding utilizing blowing in of or pneumatic changing of the coal particles, this situation is reversed. The coarser particles drop first due to the weight thereof so that the pneumatic type charging is especially adapted for furnaces in which the upper run of the travelling grate moves from the front to the rear of the furnace.

In the present invention the two different effects of the mechanical and pneumatic charging are combined to broaden the fuel program and to provide a fuel feeding arrangement for fuels with low gas content and for fine coals. With the present invention the mechanical throwing shovel is utilized for coarser particles and exclusively when the coal is of such nature with regard to particle size that it is, without any further treatment, of such size as to be adaptable for mechanical or throw-charging.

The blowing in or pneumatic installation of the present invention is, of course, more suitable for the finer grain particles of the fuel and with the cooperation of both arrangements the fuel feeding, in accordance with the nited States Patent O ICC present invention, makes allowance for the nature and quality the fuel to be fired and provides for the most economical mode of operation.

In pneumatic charging the air pressure must be such that the fine particles are carried a sufiicient distance into the firing space. This requires a greater expenditure of energy when compared with an arrangement in which a mechanical charging device is employed. Therefore,'it is seen that with the present fuel feeding arrangement the pneumatic or blow-in fuel feeding is effective for only a part of the total fuel and therefore the energy expended is not as high as when fuel is charged exclusively with pneumatic means. Preferably in the present invention, the blow-in or pneumatic fuel feeding means is disposed below the mechanical fuel feeding arrangement.

Accordingly, it is one object of the present invention to provide fuel feeding arrangements in which fuel, regardless of particle size, can be utilized and in which the fuel is charged to the furnace by separate means in accordance with the size of the grains thereof.

It is a further object of the invention to provide an arrangement in which fuel is fed from a bunker to the charging means and in which separating means are combined with the charging means to retain large size particles in a position to be charged by the mechanical throw-in device and to permit the finer particles to pass to an area adjacent the nozzle of the pneumatic charger so that the fine particles are blown into the furnace.

It is a further object to provide the separating means in the form of a grate to provide a sieve or separating effect on the fuel.

It is therefore seen that with the arrangement in accordance with the invention, the common simultaneous application of the'principles of mechanical charging and pneumatic charging results in an extension of the fuel program and provides further that the grain limit be- Figure 3 is a transverse section through the separating grate;

Figure 4 is a horizontal diagrammatic section of part of the pneumatic charging arrangement and Figure 5 is a diagrammatic view illustrating the height adjustment of the grate rods.

In Figure 1 so much of the furnace structure as is necessary to illustrate the principles of the invention has been disclosed and in connection with which, the reference character a denotes the travelling grate of the type in which the'upper run travels from the rear toward the front wall of the furnace to discharge ashes adjacent the front; b diagrammatically denotes the completely tube filled firing space. The mechanical or throw-charging arrangement is denoted generally by c while the pressure conduit for the pneumatic charging is denoted by a'.

In Figure 2, the arrangement is illustrated on a larger scale and as disclosed, the fuel feeding devices are op erably associated with the front wall of the furnace. The fuel passes from the hopper h through a fuel distributing wheel or roller i operative to adjust the quantity of fuel and from thence falls upon the grate or sieve associated with the feeding arrangement and constituted by the grate bars g of wedge shape cross section. The larger particles that do not pass between the grate bars are thrown by the movable throw shovel or feeding device k into the firing space by known arrangements, for example by spring pressure acting upon a driven throwing member. Through the slotsv or spaces between the grate bars the finer grain portions of the fuel drop into the scattering member I from whence it is blown into the fire from the nozzle 11 of the pneumatic feeding arrangement. As shown in Figures 2 and 4 the nozzle 11 is a continuation of the cylindrical tube section m and is of reduced vertical dimensions and of a flared mouth structure and the scattering surface 1 forms a substantial continuation of the lateral flaring of the mouth of the nozzle n. In order to increase the sieve or separating effect of the sepa ng grate, the bars are alternatively fixed and rcciprocable. As indicated, slots are provided in the rods whereby every second rod can be moved to and from the furnace wall by connecting rod mechanism connected at the outer ends of the bars and driven by an eccentric. If desired, all of the grate bars may be movably mounted and alternate bars movable in opposite relation to one another.

Furthermore, and as disclosed in Figure 5, in order to adapt the grain separation to fine grain particles of coal and to regulate the fineness thereof, the grate bars are adjustable in height so that, therefore, the grate slots between 21 and 22 may be varied.

It is therefore seen that an arrangement is provided in which the fuel is sieved or separated at the feeding area and as the fine particles are falling from the grate they are blown into the furnace, the throw-in shovel hurling the larger particles to an area adjacent the rear end of the travelling grate.

It is therefore apparent from the foregoing description that the present invention provides a fuel feeding arrangement in which coal fed to the throw charger k is retained by the flat upper surfaces of the grate bars g when the particles size is larger than the space between the bars and this large grained or large size coal is charged mechanically. The smaller particles pass between the grate bars and are blown into the furnace in the examples of Figures 1 and 2. Thus the invention provides coal separation immediately adjacent the fuel feeding orifice in which the separating means effectively divide the orifice into individual passages for large particles and small particles. The movement of the grate bars accelerates the separation and the adjust ment of the height of some of these bars varies the degree of fineness of the particles blown in pneumatically.

It is further noted that the arrangement is such that either fuel feeding means can be operated independently of the other if the coal originally is of a particle size that is adaptable for either mechanical or pneumatic charging. Thus the retraction of the plate v coal is fed only to the pneumatic in Figures 1 and 2 if the original particle size of the coal particles is greater than the space between the grate bars only the mechanical charger will be utilized. Likewise in Figures 1 and 2 if very fine particles are initially fed from the hopper 11 they will all pass through the grate bars and will be blown into the furnace.

It is believed therefore that the present invention possesses inherent structural features as regards the economy of operation of the fuel feeding of a furnace. Particularly in the arrangement of Figures 1 and 2 the separation takes place immediately adjacent the feed outlet. It is clear, therefore, that my invention provides fuel feeding means for a furnace effectively operable regardless of the particle size of the fuel to be fed and one which, therefore, in operation aids maximum results in the expenditure of a minimum amount of energy.

The path of the fuel as it is charged to the furnace may be seen from Figure 1. Figure 2 discloses in dotted lines the throw shovel k in the starting and end positions, and the device for moving the grate bars g to and fro. Means for adjusting the bars g vertically are shown in Figure 5. Said means comprise a girder 11 carrying the bars g; the girder 1 may be lifted or lowered by a cam disk 2 which is adjustable by a handle 3.

Having described my invention, what is desired to be secured by Letters Patent is:

1. In a furnace structure, a front and rear Wall, an endless travelling grate within the furnace having its upper run movable from the rear toward the front wall, a combustion chamber above the grate, means for receiving fuel to be burnt mounted adjacent the exterior of the front wall, plural fuel feeding means embodied with the front wall abov the level of said grate and including a mechanical throw charging means and pneumatic feeding means both directed toward the rear wall of the furnace for feeding at least part of the fuel, one of the said fuel feeding means being disposed above the other, means for leading the fuel from the fuel receiving means to the feeding means, fuel separating means embodied with the fuel feeding means and located exteriorly of the combustion chamber to grade the fuel according to particle size comprising a grate embodying a plurality of spaced grate bars and the throw charging device being above the grate and operative to eject fuel of a particle size greater than the space between the grate bars, the pneumatic feeding means including at least one nozzle disposed beneath the grate and means providing a surface beneath the grate in front of the nozzle to receive fine grain particles of fuel to be fed to the furnace by the pneumatic feeding means.

2. A furnace structure as defined in and by claim 1 in which the bars of the grate are movable.

3. A furnace structure as defined in and by claim 2 in which the bars of the grate are reciprocable.

4. A furnace structure as defined in and by claim 3 in which the bars of the grate are Wedge shaped in cross section and nonadjacent bars are reciprocable in a vertical direction to vary the height thereof to thereby vary the slot width between adjacent bars to vary the degree of fineness of the particles passing through the grate.

5. A furnace structure including oppositely disposed spaced walls, fuel charging means cooperatively associated with one of said walls and an endless grate movable between the walls with the upper run moving toward the wall with which the fuel charging means are associated, said fuel charging means including means to receive fuel to be burnt, a movable throw shovel, at least one opening through the adjacent wall of the furnace, a separating grate cooperatively associated with and disposed subjacent said throw shovel to receive fuel, said separating grate including spaced bars so that small size particles pass between the bars and large particles are retained thereby for ejection by the throw shovel into the furnace, means defining a scattering surface spaced from and beneath the bars of said separating grate, said surface communicating with the interior of the furnace and a pneumatic feed means in communication with said surface to blow fine particles therefrom into the furnace.

6. A furnace structure as defined in and by claim 5 in which said throw shovel is oscillatable in a direction to and from the interior of the furnace about an axis above said separating grate, said separating grate including a plurality of bars of wedge shaped cross section with the upper surface of the bars being wider than the lower surface, and at least some of said bars being movable to accelerate separating action of fuel coming in contact therewith.

References Qited in the file of this patent UNITED STATES PATENTS 1,510,045 Day Sept. 30, 1924 (Other references on following page) UNITED STATES PATENTS FOREIGN PATENTS Great Britain Oct. 9, 1895 Germany June 18, 1928 Germany June 27, 1936 Germany Oct. 10, 1938 Great Britain Mar. 9, 1948 

